Old zircons

Ancient crystals suggest early Earth had land and freshwater
"The zircons represent a rare report from the mysterious Hadean, the geological time period that ended about 4 billion years ago, 500 million years after Earth’s formation. The planet, originally a ball of magma, had cooled off and formed a crust. Somehow, perhaps from a bombardment of water-rich asteroids, it had accumulated a global ocean. Earth may have remained watery for quite some time—at least until tectonic processes began to recycle Earth’s crust into its interior, and magma bubbled up in chains of island volcanoes that eventually fused into continents.
Much of this is guesswork, because almost no rock survives from the Hadean. The oldest rock with a reliable age—a gneiss from Canada—is 4.03 billion years old. The only surviving material from before then are zircons, found embedded in younger rock, which are as much as 4.4 billion years old. “Just about any information that we can get from these Hadean zircons is useful because it’s our singular record of the Earth’s first 500 million years,” says geologist Stephen Mojzsis of the HUN-REN Research Centre for Astronomy and Earth Sciences."
https://www.science.org/content/article/ancient-crystals-suggest-early-earth-had-land-and-freshwater